HLA-DR expression and disease activity in ulcerative colitis

Epithelial expression of HLA, secretory component (poly-Ig receptor), and adhesion molecules in the human alimentary tract

Epithelial HLA class II is differentially expressed (DR >> DP) only after birth in salivary glands and small intestinal mucosa, in contrast to class I determinants and secretory component (SC) which appear early in gestation. However, there is a brisk postnatal increase in SC expression along with the class II induction, suggesting stimulation by cytokines from activated immune cells. T lymphocytes remain quite scanty in postnatal salivary glands, and the striking SC and class II expression might reflect a synergistic effect of IFN-gamma and TFN-alpha on immature epithelial cells. Enhanced epithelial expression of both SC and class II in salivary glands from sudden infant death victims could be the effect of immunostimulation caused by an infectious agent. Strikingly upregulated SC and epithelial class II expression (DR > DP > DQ) is seen in various inflammatory lesions such as obstructive sialadenitis, Sjögren's syndrome, chronic gastritis, and celiac disease. IFN-gamma and TNF-alpha are most likely involved as the expression patterns can be reproduced with these cytokines in vitro on colonic epithelial cell lines. However, these molecules of the Ig supergene family do not show a selective response in epithelia of inflammatory lesions because increased expression is also seen for lysozyme, lactoferrin and some other proteins. ICAM-1 can be upregulated on epithelial cells by various cytokines in vitro although the situation remains uncertain in mucosal inflammation. The expression pattern in IBD is complicated by dysplastic epithelial changes leading to reduced SC levels which may thus, in turn, jeopardize the poly-Ig transport mechanism. Epithelial class II molecules appear to have antigen-presenting properties, but the immunopathologic role of their increased expression in inflammatory disease in terms of induction of autoimmunity and/or abrogation of oral tolerance is a matter of continuing dispute.

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Heterogeneous epithelial expression of class II (HLA-DR) determinants and secretory component related to dysplasia in ulcerative colitis

The intensity and degree of heterogeneous epithelial marker expression were evaluated immunohistochemically in 29 mucosal biopsy specimens from 7 ulcerative colitis (UC) patients with dysplasia. Biopsy specimens from UC patients with mild (n = 7) or severe (n = 6) inflammation and from histologically normal samples (n = 7) served as controls. HLA-DR showed heterogeneous epithelial expression in all lesions with high grade dysplasia and in 6 of 8 with low grade dysplasia. SC was heterogeneous stained in 17 of 21 lesions with high grade dysplasia and in all but two lesions with low grade dysplasia. In histologically normal mucosa, SC was homogeneously expressed and epithelial DR was virtually absent. In mildly inflamed UC lesions, SC exhibited patchy distribution in only one sample and DR in two, whereas both SC and DR showed a slight degree of heterogeneous expression in all lesions with severe inflammation. Moreover, the overall intensity of SC staining tended to decrease with increasing degree of inflammation, whereas the opposite was seen for DR. Decreased SC and increased DR expression thus seemed to be related to intensified inflammatory activity, whereas heterogeneous expression of these markers was significantly more related to dysplasia.

Expression of HLA-DR antigens on colonic epithelium in ulcerative colitis

Although the expression of HLA-DR antigens on colonic epithelium in ulcerative colitis has been observed by several groups, the results of the expression in remission have been conflicting and there has been virtually no study concerning the expression in non-inflamed area in active ulcerative colitis. We studied systematically HLA-DR expression on colonic epithelium in 37 patients with ulcerative colitis chronologically, namely in remission as well as in the active stage and inflamed and non-inflamed areas simultaneously in the active stage. HLA-DR antigens were detected by indirect peroxidase staining using anti-HLA-DR monoclonal antibody. We confirmed the previous observation that epithelium from control colon does not express HLA-DR antigens, while epithelium from ulcerative colitis expresses the antigens with high frequency (83.3 percent). In addition, we demonstrated that HLA-DR expression on colonic epithelium in active ulcerative colitis disappeared in remission. Our new finding was that there is no HLA-DR expression on colonic epithelium in non-inflamed mucosa in active ulcerative colitis. Namely HLA-DR antigens were expressed only on inflamed epithelium of ulcerative colitis. These results lead to the conclusion that the expression of HLA-DR antigens on colonic epithelium in ulcerative colitis is closely related to the inflammation of mucosa.